Electronic ophthalmic lens with rear-facing pupil diameter sensor

ABSTRACT

A rear-facing pupil diameter sensing system for an ophthalmic lens comprising an electronic system is described herein. The rear-facing pupil diameter sensing system is part of an electronic system incorporated into the ophthalmic lens. The electronic system includes one or more batteries or other power sources, power management circuitry, one or more sensors, clock generation circuitry, control algorithms and circuitry, and lens driver circuitry. The rear-facing pupil diameter sensing system is utilized to determine pupil position and use this information to control various aspects of the ophthalmic lens.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a powered or electronic ophthalmic lenshaving a sensor and associated hardware and software for detectingand/or sensing pupil diameter, and more particularly, to a sensor andassociated hardware and software for detecting changes in pupil diameterand changing the state of an electronic ophthalmic lens.

2. Discussion of the Related Art

As electronic devices continue to be miniaturized, it is becomingincreasingly more likely to create wearable or embeddablemicroelectronic devices for a variety of uses. Such uses may includemonitoring aspects of body chemistry, administering controlled dosagesof medications or therapeutic agents via various mechanisms, includingautomatically, in response to measurements, or in response to externalcontrol signals, and augmenting the performance of organs or tissues.Examples of such devices include glucose infusion pumps, pacemakers,defibrillators, ventricular assist devices and neurostimulators. A new,particularly useful field of application is in ophthalmic wearablelenses and contact lenses. For example, a wearable lens may incorporatea lens assembly having an electronically adjustable focus to augment orenhance performance of the eye. In another example, either with orwithout adjustable focus, a wearable contact lens may incorporateelectronic sensors to detect concentrations of particular chemicals inthe precorneal (tear) film. The use of embedded electronics in a lensassembly introduces a potential requirement for communication with theelectronics, for a method of powering and/or re-energizing theelectronics, for interconnecting the electronics, for internal andexternal sensing and/or monitoring, and for control of the electronicsand the overall function of the lens.

The human eye has the ability to discern millions of colors, adjusteasily to shifting light conditions, and transmit signals or informationto the brain at a rate exceeding that of a high-speed internetconnection. Lenses, such as contact lenses and intraocular lenses,currently are utilized to correct vision defects such as myopia(nearsightedness), hyperopia (farsightedness), presbyopia andastigmatism. However, properly designed lenses incorporating additionalcomponents may be utilized to enhance vision as well as to correctvision defects.

Contact lenses may be utilized to correct myopia, hyperopia, astigmatismas well as other visual acuity defects. Contact lenses may also beutilized to enhance the natural appearance of the wearer's eyes. Contactlenses or “contacts” are simply lenses placed on the anterior surface ofthe eye. Contact lenses are considered medical devices and may be wornto correct vision and/or for cosmetic or other therapeutic reasons.Contact lenses have been utilized commercially to improve vision sincethe 1950s. Early contact lenses were made or fabricated from hardmaterials, were relatively expensive and fragile. In addition, theseearly contact lenses were fabricated from materials that did not allowsufficient oxygen transmission through the contact lens to theconjunctiva and cornea which potentially could cause a number of adverseclinical effects. Although these contact lenses are still utilized, theyare not suitable for all patients due to their poor initial comfort.Later developments in the field gave rise to soft contact lenses, basedupon hydrogels, which are extremely popular and widely utilized today.Specifically, silicone hydrogel contact lenses that are available todaycombine the benefit of silicone, which has extremely high oxygenpermeability, with the proven comfort and clinical performance ofhydrogels. Essentially, these silicone hydrogel based contact lenseshave higher oxygen permeability and are generally more comfortable towear than the contact lenses made of the earlier hard materials.

Conventional contact lenses are polymeric structures with specificshapes to correct various vision problems as briefly set forth above. Toachieve enhanced functionality, various circuits and components have tobe integrated into these polymeric structures. For example, controlcircuits, microprocessors, communication devices, power supplies,sensors, actuators, light-emitting diodes, and miniature antennas may beintegrated into contact lenses via custom-built optoelectroniccomponents to not only correct vision, but to enhance vision as well asprovide additional functionality as is explained herein. Electronicand/or powered contract lenses may be designed to provide enhancedvision via zoom-in and zoom-out capabilities, or just simply modifyingthe refractive capabilities of the lenses. Electronic and/or poweredcontact lenses may be designed to enhance color and resolution, todisplay textural information, to translate speech into captions in realtime, to offer visual cues from a navigation system, and to provideimage processing and internet access. The lenses may be designed toallow the wearer to see in low-light conditions. The properly designedelectronics and/or arrangement of electronics on lenses may allow forprojecting an image onto the retina, for example, without avariable-focus optic lens, provide novelty image displays and evenprovide wakeup alerts. Alternately, or in addition to any of thesefunctions or similar functions, the contact lenses may incorporatecomponents for the noninvasive monitoring of the wearer's biomarkers andhealth indicators. For example, sensors built into the lenses may allowa diabetic patient to keep tabs on blood sugar levels by analyzingcomponents of the tear film without the need for drawing blood. Inaddition, an appropriately configured lens may incorporate sensors formonitoring cholesterol, sodium, and potassium levels, as well as otherbiological markers. This, coupled with a wireless data transmitter,could allow a physician to have almost immediate access to a patient'sblood chemistry without the need for the patient to waste time gettingto a laboratory and having blood drawn. In addition, sensors built intothe lenses may be utilized to detect light incident on the eye tocompensate for ambient light conditions or for use in determining blinkpatterns.

The proper combination of devices could yield potentially unlimitedfunctionality; however, there are a number of difficulties associatedwith the incorporation of extra components on a piece of optical-gradepolymer. In general, it is difficult to manufacture such componentsdirectly on the lens for a number of reasons, as well as mounting andinterconnecting planar devices on a non-planar surface. It is alsodifficult to manufacture to scale. The components to be placed on or inthe lens need to be miniaturized and integrated onto just 1.5 squarecentimeters of a transparent polymer while protecting the componentsfrom the liquid environment on the eye. It is also difficult to make acontact lens comfortable and safe for the wearer with the addedthickness of additional components.

Given the area and volume constraints of an ophthalmic device such as acontact lens, and the environment in which it is to be utilized, thephysical realization of the device must overcome a number of problems,including mounting and interconnecting a number of electronic componentson a non-planar surface, the bulk of which comprises optic plastic.Accordingly, there exists a need for providing a mechanically andelectrically robust electronic contact lens.

As these are powered lenses, energy or more particularly currentconsumption, to run the electronics is a concern given batterytechnology on the scale for an ophthalmic lens. In addition to normalcurrent consumption, powered devices or systems of this nature generallyrequire standby current reserves, precise voltage control and switchingcapabilities to ensure operation over a potentially wide range ofoperating parameters, and burst consumption, for example, up to eighteen(18) hours on a single charge, after potentially remaining idle foryears. Accordingly, there exists a need for a system that is optimizedfor low-cost, long-term reliable service, safety and size whileproviding the required power.

In addition, because of the complexity of the functionality associatedwith a powered lens and the high level of interaction between all of thecomponents comprising a powered lens, there is a need to coordinate andcontrol the overall operation of the electronics and optics comprising apowered ophthalmic lens.

Accordingly, there is a need for a system to control the operation ofall of the other components that is safe, low-cost, and reliable, has alow rate of power consumption and is scalable for incorporation into anophthalmic lens.

Powered or electronic ophthalmic lenses may have to account for certainunique physiological functions from the individual utilizing the poweredor electronic ophthalmic lens. More specifically, powered lenses mayhave to account for blinking, including the number of blinks in a giventime period, the duration of a blink, the time between blinks and anynumber of possible blink patterns, for example, if the individual isdosing off. Blink detection may also be utilized to provide certainfunctionality, for example, blinking may be utilized as a means tocontrol one or more aspects of a powered ophthalmic lens. Additionally,external factors, such as changes in light intensity levels, and theamount of visible light that a person's eyelid blocks out, have to beaccounted for when determining blinks. For example, if a room has anillumination level between fifty-four (54) and one hundred sixty-one(161) lux, a photosensor should be sensitive enough to detect lightintensity changes that occur when a person blinks.

Ambient light sensors or photosensors are utilized in many systems andproducts, for example, on televisions to adjust brightness according tothe room light, on lights to switch on at dusk, and on phones to adjustthe screen brightness.

However, these currently utilized sensor systems are not small enoughand/or do not have low enough power consumption for incorporation intocontact lenses.

It is also important to note that different types of blink detectors maybe implemented with computer vision systems directed at one's eye(s),for example, a camera digitized to a computer. Software running on thecomputer can recognize visual patterns such as the eye open and closed.These systems may be utilized in ophthalmic clinical settings fordiagnostic purposes and studies. Unlike the above described detectorsand systems, these systems are intended for off eye use and to look atrather than look away from the eye. Although these systems are not smallenough to be incorporated into contact lenses, the software utilized maybe similar to the software that would work in conjunction with poweredcontact lenses. Either system may incorporate software implementationsof artificial neural networks that learn from input and adjust theiroutput accordingly. Alternately, non-biology based softwareimplementations incorporating statistics, other adaptive algorithms,and/or signal processing may be utilized to create smart systems.

Accordingly, there exists a need for a means and method for detectingcertain physiological functions, such as a blink, and utilizing them toactivate and/or control an electronic or powered ophthalmic lensaccording to the type of blink sequence detected by a sensor. The sensorbeing utilized having to be sized and configured for use in a contactlens.

Alternately, pupil diameter rather than or in addition to blinking maybe utilized to control the functionality of a contact lens under certainconditions. Pupil diameter is a measurable parameter of the eye whichmay be used to command changes in ophthalmic devices. Pupil diameter maybe measured, for example, by a camera facing the eye. The cameracaptures images of the eye, determines the pupil through image, pattern,or contrast recognition, and calculates pupil diameter. Pupil diameter,whether dilated or constricted, is correlated with the level of lightincident on the eye, focusing up-close as opposed to far away, and somemedical conditions. Ophthalmic devices could change light transmissionor focal length based on pupil diameter, or trigger other events.Alternately, the sensed data may be simply collected and utilized formonitoring medical conditions.

Existing methods and devices for measuring pupil diameter are notsuitable for use in contact lenses. For example, cameras and recognitionsystems are typically found in clinical settings or perhaps on spectaclelenses. Existing systems have neither the small size nor the low currentnecessary for integration into a contact lens. Existing systems are alsonot intended to vary the state of an ophthalmic device based on changesin pupil diameter. Accordingly, there exists a need for a means andmethod for detecting pupil diameter and utilizing this information tocontrol an electronic or powered ophthalmic lens.

SUMMARY OF THE INVENTION

The electronic ophthalmic lens with rear-facing pupil dilation sensor inaccordance with the present invention overcomes the limitationsassociated with the prior art as briefly described above.

In accordance with one aspect, the present invention is directed to apowered ophthalmic lens. The powered ophthalmic lens comprises a contactlens including an optic zone and a peripheral zone, and a pupil diametersensor system incorporated into the contact lens for measuring pupildiameter, the pupil diameter sensor system including at least onesensor, a system controller operatively associated with the at least onesensor and configured for determining the diameter of the pupil andoutput a control signal based on pupil diameter, and at least oneactuator configured to receive the output control signal and implement apredetermined function.

The present invention relates to a powered contact lens comprising anelectronic system, which performs any number of functions, includingactuating a variable-focus optic if included. The electronic systemincludes one or more batteries or other power sources, power managementcircuitry, one or more sensors, clock generation circuitry, controlalgorithms and circuitry, and lens driver circuitry.

Control of a powered ophthalmic lens may be accomplished through amanually operated external device that communicates with the lenswirelessly, such as a hand-held remote unit. Alternately, control of thepowered ophthalmic lens may be accomplished via feedback or controlsignals directly from the wearer. For example, sensors built into thelens may detect blinks and/or blink patterns. Based upon the pattern orsequence of blinks, the powered ophthalmic lens may change state, forexample, its refractive power in order to either focus on a near objector a distant object. In another alternate exemplary embodiment, controlof the powered ophthalmic lens may be accomplished via feedback orcontrol signals directly from the wearer; namely, through detectedchanges in the size of the individual's pupils.

The pupil diameter sensor of the present invention is of the appropriatesmall size and low current consumption to be integrated into a contactlens. In one exemplary embodiment, the sensor is fabricated with asilicon semiconductor process, thinned to approximately one hundred(100) microns or less, and diced to a die size of approximately 300×300microns or less. In an alternate exemplary embodiment, the sensor isfabricated as a thin, flexible device which conforms to the sphericalshape of a contact lens. In yet another exemplary embodiment, the sensoris fabricated as an array of smaller sensors placed at various locationsin the contact lens to sample various points on the iris. Sensors maydetermine pupil diameter and changes thereof by detecting lightreflection, impedance, electromagnetic field, neural activity, muscleactivity, and other parameters as are known in the ophthalmic art.

The pupil diameter sensor is designed to consume low current, permittingoperation in a contact lens from a small battery and/or energyharvester. In one exemplary embodiment, the sensor is implemented as anunbiased or low-biased photosensor detecting light reflecting off theiris. The sensor in this case may be sampled at a low duty cycle and lowfrequency such that total power consumption is minimized. In anotherexemplary embodiment, the sensor is implemented to detect impedanceacross through the iris or at various points on the iris. Again, thesensor is implemented using low-current technique as are common in theart, for example, high impedance and low voltage. In yet anotherexemplary embodiment, the sensor is implemented to measure neuromuscularactivity, for example, by sensing the electromagnetic emissions from themuscles which control the iris aperture.

The pupil diameter sensor is designed to operate in a system whichtriggers the electronic ophthalmic device based on pupil diameterchanges. In one exemplary embodiment, the sensor is sampled a rate whichis fast enough to comfortable and conveniently detect the desire tochange focal length, but slow enough to minimize current consumption foroperation off a small battery and/or energy harvester. The sensor isincluded in a system to consider pupil diameter along with other inputs,for example, ambient light incident on the eye. In this case, the systemcould detect changes in pupil diameter in the absence of a decrease inambient light, a situation correlated with the desire to focus up-close.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other features and advantages of the invention will beapparent from the following, more particular description of preferredembodiments of the invention, as illustrated in the accompanyingdrawings.

FIG. 1 illustrates an exemplary contact lens comprising a blinkdetection system in accordance with some embodiments of the presentinvention.

FIG. 2 illustrates a graphical representation of light incident on thesurface of the eye versus time, illustrating a possible involuntaryblink pattern recorded at various light intensity levels versus time anda usable threshold level based on some point between the maximum andminimum light intensity levels in accordance with the present invention.

FIG. 3 is an exemplary state transition diagram of a blink detectionsystem in accordance with the present invention.

FIG. 4 is a diagrammatic representation of a photodetection pathutilized to detect and sample received light signals in accordance withthe present invention.

FIG. 5 is a block diagram of digital conditioning logic in accordancewith the present invention.

FIG. 6 is a block diagram of digital detection logic in accordance withthe present invention.

FIG. 7 is an exemplary timing diagram in accordance with the presentinvention.

FIG. 8 is a diagrammatic representation of a digital system controllerin accordance with the present invention.

FIGS. 9A through 9G are exemplary timing diagrams for automatic gaincontrol in accordance with the present invention.

FIG. 10 is a diagrammatic representation of light-blocking andlight-passing regions on an exemplary integrated circuit die inaccordance with the present invention.

FIG. 11 is a diagrammatic representation of an exemplary electronicinsert, including a blink detector, for a powered contact lens inaccordance with the present invention.

FIG. 12 is a diagrammatic representation of a powered ophthalmic lenshaving a first exemplary pupil diameter sensor positioned on eye inaccordance with the present invention.

FIG. 13 is a diagrammatic representation of a powered ophthalmic lenshaving a second exemplary pupil diameter sensor positioned on eye inaccordance with the present invention.

FIG. 14 is a block diagram representation of an electronic system fordetecting and utilizing pupil diameter in accordance with the presentinvention.

FIG. 15 is a plot of ambient light and pupil diameter versus time inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Conventional contact lenses are polymeric structures with specificshapes to correct various vision problems as briefly set forth above. Toachieve enhanced functionality, various circuits and components may beintegrated into these polymeric structures. For example, controlcircuits, microprocessors, communication devices, power supplies,sensors, actuators, light-emitting diodes, and miniature antennas may beintegrated into contact lenses via custom-built optoelectroniccomponents to not only correct vision, but to enhance vision as well asprovide additional functionality as is explained herein. Electronicand/or powered contact lenses may be designed to provide enhanced visionvia zoom-in and zoom-out capabilities, or just simply modifying therefractive capabilities of the lenses. Electronic and/or powered contactlenses may be designed to enhance color and resolution, to displaytextural information, to translate speech into captions in real time, tooffer visual cues from a navigation system, and to provide imageprocessing and internet access. The lenses may be designed to allow thewearer to see in low light conditions. The properly designed electronicsand/or arrangement of electronics on lenses may allow for projecting animage onto the retina, for example, without a variable focus optic lens,provide novelty image displays and even provide wakeup alerts.Alternately, or in addition to any of these functions or similarfunctions, the contact lenses may incorporate components for thenoninvasive monitoring of the wearer's biomarkers and health indicators.For example, sensors built into the lenses may allow a diabetic patientto keep tabs on blood sugar levels by analyzing components of the tearfilm without the need for drawing blood. In addition, an appropriatelyconfigured lens may incorporate sensors for monitoring cholesterol,sodium, and potassium levels, as well as other biological markers. Thiscoupled with a wireless data transmitter could allow a physician to havealmost immediate access to a patient's blood chemistry without the needfor the patient to waste time getting to a laboratory and having blooddrawn. In addition, sensors built into the lenses may be utilized todetect light incident on the eye to compensate for ambient lightconditions or for use in determining blink patterns.

The powered or electronic contact lens of the present inventioncomprises the necessary elements to correct and/or enhance the vision ofpatients with one or more of the above described vision defects orotherwise perform a useful ophthalmic function. In addition, theelectronic contact lens may be utilized simply to enhance normal visionor provide a wide variety of functionality as described above. Theelectronic contact lens may comprise a variable focus optic lens, anassembled front optic embedded into a contact lens or just simplyembedding electronics without a lens for any suitable functionality. Theelectronic lens of the present invention may be incorporated into anynumber of contact lenses as described above. In addition, intraocularlenses may also incorporate the various components and functionalitydescribed herein. However, for ease of explanation, the disclosure willfocus on an electronic contact lens to correct vision defects intendedfor single-use daily disposability.

The present invention may be employed in a powered ophthalmic lens orpowered contact lens comprising an electronic system, which actuates avariable-focus optic or any other device or devices configured toimplement any number of numerous functions that may be performed. Theelectronic system includes one or more batteries or other power sources,power management circuitry, one or more sensors, clock generationcircuitry, control algorithms and circuitry, and lens driver circuitry.The complexity of these components may vary depending on the required ordesired functionality of the lens.

Control of an electronic or a powered ophthalmic lens may beaccomplished through a manually operated external device thatcommunicates with the lens, such as a hand-held remote unit. Forexample, a fob may wirelessly communicate with the powered lens basedupon manual input from the wearer. Alternately, control of the poweredophthalmic lens may be accomplished via feedback or control signalsdirectly from the wearer. For example, sensors built into the lens maydetect blinks and/or blink patterns. Based upon the pattern or sequenceof blinks, the powered ophthalmic lens may change state, for example,its refractive power in order to either focus on a near object or adistant object.

Alternately, blink detection in a powered or electronic ophthalmic lensmay be used for other various uses where there is interaction betweenthe user and the electronic contact lens, such as activating anotherelectronic device, or sending a command to another electronic device.For example, blink detection in an ophthalmic lens may be used inconjunction with a camera on a computer wherein the camera keeps trackof where the eye(s) moves on the computer screen, and when the userexecutes a blink sequence that it detected, it causes the mouse pointerto perform a command, such as double-clicking on an item, highlightingan item, or selecting a menu item.

A blink detection algorithm is a component of the system controllerwhich detects characteristics of blinks, for example, is the lid open orclosed, the duration of the blink, the inter-blink duration, and thenumber of blinks in a given time period. The algorithm in accordancewith the present invention relies on sampling light incident on the eyeat a certain sample rate. Pre-determined blink patterns are stored andcompared to the recent history of incident light samples. When patternsmatch, the blink detection algorithm may trigger activity in the systemcontroller, for example, to activate the lens driver to change therefractive power of the lens.

Blinking is the rapid closing and opening of the eyelids and is anessential function of the eye. Blinking protects the eye from foreignobjects, for example, individuals blink when objects unexpectedly appearin proximity to the eye. Blinking provides lubrication over the anteriorsurface of the eye by spreading tears. Blinking also serves to removecontaminants and/or irritants from the eye. Normally, blinking is doneautomatically, but external stimuli may contribute as in the case withirritants. However, blinking may also be purposeful, for example, forindividuals who are unable to communicate verbally or with gestures canblink once for yes and twice for no. The blink detection algorithm andsystem of the present invention utilizes blinking patterns that cannotbe confused with normal blinking response. In other words, if blinkingis to be utilized as a means for controlling an action, then theparticular pattern selected for a given action cannot occur at random;otherwise inadvertent actions may occur. As blink speed may be affectedby a number of factors, including fatigue, eye injury, medication anddisease, blinking patterns for control purposes preferably account forthese and any other variables that affect blinking. The average lengthof involuntary blinks is in the range of about one hundred (100) to fourhundred (400) milliseconds. Average adult men and women blink at a rateof ten (10) involuntary blinks per minute, and the average time betweeninvoluntary blinks is about 0.3 to seventy (70) seconds.

An exemplary embodiment of the blink detection algorithm may besummarized in the following steps.

1. Define an intentional “blink sequence” that a user will execute forpositive blink detection.

2. Sample the incoming light level at a rate consistent with detectingthe blink sequence and rejecting involuntary blinks.

3. Compare the history of sampled light levels to the expected “blinksequence,” as defined by a blink template of values.

4. Optionally implement a blink “mask” sequence to indicate portions ofthe template to be ignored during comparisons, e.g. near transitions.This may allow for a user to deviate from a desired “blink sequence,”such as a plus or minus one (1) error window, wherein one or more oflens activation, control, and focus change can occur. Additionally, thismay allow for variation in the user's timing of the blink sequence.

An exemplary blink sequence may be defined as follows:

1. blink (closed) for 0.5 s

2. open for 0.5 s

3. blink (closed) for 0.5 s

At a one hundred (100) ms sample rate, a twenty (20) sample blinktemplate is given by

-   -   blink_template=[1,1,1, 0,0,0,0,0, 1,1,1,1,1, 0,0,0,0,0, 1,1].

The blink mask is defined to mask out the samples just after atransition (0 to mask out or ignore samples), and is given by

-   -   blink_mask=[1,1,1, 0,1,1,1,1, 0,1,1,1,1, 0,1,1,1,1, 0,1].

Optionally, a wider transition region may be masked out to allow formore timing uncertainty, and is given by

-   -   blink_mask=[1,1,0, 0,1,1,1,0, 0,1,1,1,0, 0,1,1,1,0, 0,1].

Alternate patterns may be implemented, e.g. single long blink, in thiscase a 1.5 s blink with a 24-sample template, given by

-   -   blink_template=[1,1,1,1,0,0, 0,0,0,0,0,0, 0,0,0,0,0,0,        0,1,1,1,1,1].

It is important to note that the above example is for illustrativepurposes and does not represent a specific set of data.

Detection may be implemented by logically comparing the history ofsamples against the template and mask. The logical operation is toexclusive-OR (XOR) the template and the sample history sequence, on abitwise basis, and then verify that all unmasked history bits match thetemplate. For example, as illustrated in the blink mask samples above,in each place of the sequence of a blink mask that the value is logic 1,a blink has to match the blink mask template in that place of thesequence. However, in each place of the sequence of a blink mask thatthe value is logic 0, it is not necessary that a blink matches the blinkmask template in that place of the sequence. For example, the followingBoolean algorithm equation, as coded in MATLAB®, may be utilized.

-   -   matched=not (blink_mask)|not (xor (blink_template,        test_sample)),        wherein test_sample is the sample history. The matched value is        a sequence with the same length as the blink template, sample        history and blink_mask. If the matched sequence is all logic        1's, then a good match has occurred. Breaking it down, not (xor        (blink_template, test_sample)) gives a logic 0 for each mismatch        and a logic 1 for each match. Logic oring with the inverted mask        forces each location in the matched sequence to a logic 1 where        the mask is a logic 0. Accordingly, the more places in a blink        mask template where the value is specified as logic 0, the        greater the margin of error in relation to a person's blinks is        allowed. MATLAB® is a high level language and implementation for        numerical computation, visualization and programming and is a        product of MathWorks, Natick, Mass. It is also important to note        that the greater the number of logic 0's in the blink mask        template, the greater the potential for false positive matched        to expected or intended blink patterns. It should be appreciated        that a variety of expected or intended blink patterns may be        programmed into a device with one or more active at a time. More        specifically, multiple expected or intended blink patterns may        be utilized for the same purpose or functionality, or to        implement different or alternate functionality. For example, one        blink pattern may be utilized to cause the lens to zoom in or        out on an intended object while another blink pattern may be        utilized to cause another device, for example, a pump, on the        lens to deliver a dose of a therapeutic agent.

FIG. 1 illustrates, in block diagram form, a contact lens 100,comprising an electronic blink detector system, in accordance with anexemplary embodiment of the present invention. In this exemplaryembodiment, the electronic blink detector system may comprise aphotosensor 102, an amplifier 104, an analog-to-digital converter or ADC106, a digital signal processor 108, a power source 110, an actuator112, and a system controller 114.

When the contact lens 100 is placed onto the front surface of a user'seye the electronic circuitry of the blink detector system may beutilized to implement the blink detection algorithm of the presentinvention. The photosensor 102, as well as the other circuitry, isconfigured to detect blinks and/or various blink patterns produced bythe user's eye.

In this exemplary embodiment, the photosensor 102 may be embedded intothe contact lens 100 and receives ambient light 101, converting incidentphotons into electrons and thereby causing a current, indicated by arrow103, to flow into the amplifier 104. The photosensor or photodetector102 may comprise any suitable device. In one exemplary embodiment, thephotosensor 102 comprises a photodiode.

In a preferred exemplary embodiment, the photodiode is implemented in acomplimentary metal-oxide semiconductor (CMOS process technology) toincrease integration ability and reduce the overall size of thephotosensor 102 and the other circuitry. The current 103 is proportionalto the incident light level and decreases substantially when thephotodetector 102 is covered by an eyelid. The amplifier 104 creates anoutput proportional to the input, with gain, and may function as atransimpedance amplifier which converts input current into outputvoltage. The amplifier 104 may amplify a signal to a useable level forthe remainder of the system, such as giving the signal enough voltageand power to be acquired by the ADC 106. For example, the amplifier maybe necessary to drive subsequent blocks since the output of thephotosensor 102 may be quite small and may be used in low-lightenvironments. The amplifier 104 may be implemented as a variable-gainamplifier, the gain of which may be adjusted by the system controller114, in a feedback arrangement, to maximize the dynamic range of thesystem. In addition to providing gain, the amplifier 104 may includeother analog signal conditioning circuitry, such as filtering and othercircuitry appropriate to the photosensor 102 and amplifier 104 outputs.The amplifier 104 may comprise any suitable device for amplifying andconditioning the signal output by the photosensor 102. For example, theamplifier 104 may simply comprise a single operational amplifier or amore complicated circuit comprising one or more operational amplifiers.As set forth above, the photosensor 102 and the amplifier 104 areconfigured to detect and isolate blink sequences based upon the incidentlight intensity received through the eye and convert the input currentinto a digital signal usable ultimately by the system controller 114.The system controller 114 is preferably preprogrammed or preconfiguredto recognize various blink sequences and/or blink patterns in variouslight intensity level conditions and provide an appropriate outputsignal to the actuator 112. The system controller 114 also comprisesassociated memory.

In this exemplary embodiment, the ADC 106 may be used to convert acontinuous, analog signal output from the amplifier 104 into a sampled,digital signal appropriate for further signal processing. For example,the ADC 106 may convert an analog signal output from the amplifier 104into a digital signal that may be useable by subsequent or downstreamcircuits, such as a digital signal processing system or microprocessor108. A digital signal processing system or digital signal processor 108may be utilized for digital signal processing, including one or more offiltering, processing, detecting, and otherwise manipulating/processingsampled data to permit incident light detection for downstream use. Thedigital signal processor 108 may be preprogrammed with the blinksequences and/or blink patterns described above. The digital signalprocessor 108 also comprises associated memory. The digital signalprocessor 108 may be implemented utilizing analog circuitry, digitalcircuitry, software, or a combination thereof. In the illustrateexemplary embodiment, it is implemented in digital circuitry. The ADC106 along with the associated amplifier 104 and digital signal processor108 are activated at a suitable rate in agreement with the sampling ratepreviously described, for example every one hundred (100) ms.

A power source 110 supplies power for numerous components comprising theblink detection system. The power may be supplied from a battery, energyharvester, or other suitable means as is known to one of ordinary skillin the art. Essentially, any type of power source 110 may be utilized toprovide reliable power for all other components of the system. A blinksequence may be utilized to change the state of the system and/or thesystem controller. Furthermore, the system controller 114 may controlother aspects of a powered contact lens depending on input from thedigital signal processor 108, for example, changing the focus orrefractive power of an electronically controlled lens through theactuator 112.

The system controller 114 uses the signal from the photosensor chain;namely, the photosensor 102, the amplifier 104, the ADC 106 and thedigital signal processing system 108, to compare sampled light levels toblink activation patterns. Referring to FIG. 2, a graphicalrepresentation of blink pattern samples recorded at various lightintensity levels versus time and a usable threshold level isillustrated. Accordingly, accounting for various factors may mitigateand/or prevent error in detecting blinks when sampling light incident onthe eye, such as accounting for changes in light intensity levels indifferent places and/or while performing various activities.Additionally, when sampling light incident on the eye, accounting forthe effects that changes in ambient light intensity may have on the eyeand eyelid may also mitigate and/or prevent error in detecting blinks,such as how much visible light an eyelid blocks when it is closed inlow-intensity light levels and in high-intensity light levels. In otherwords, in order to prevent erroneous blinking patterns from beingutilized to control, the level of ambient light is preferably accountedfor as is explained in greater detail below.

For example, in a study, it has been found that the eyelid on averageblocks approximately ninety-nine (99) percent of visible light, but atlower wavelengths less light tends to be transmitted through the eyelid,blocking out approximately 99.6 percent of visible light. At longerwavelengths, toward the infrared portion of the spectrum, the eyelid mayblock only thirty (30) percent of the incident light. What is importantto note; however, is that light at different frequencies, wavelengthsand intensities may be transmitted through the eyelids with differentefficiencies. For example, when looking at a bright light source, anindividual may see red light with his or her eyelids closed. There mayalso be variations in how much visible light an eyelid blocks based uponan individual, such as an individual's skin pigmentation. As isillustrated in FIG. 2, data samples of blink patterns across variouslighting levels are simulated over the course of a seventy (70) secondtime interval wherein the visible light intensity levels transmittedthrough the eye are recorded during the course of the simulation, and ausable threshold value is illustrated. The threshold is set at a valuein between the peak-to-peak value of the visible light intensityrecorded for the sample blink patterns over the course of the simulationat varying light intensity levels. Having the ability to preprogramblink patterns while tracking an average light level over time andadjusting a threshold may be critical to being able to detect when anindividual is blinking, as opposed to when an individual is not blinkingand/or there is just a change in light intensity level in a certainarea.

Referring now again to FIG. 1, in further alternate exemplaryembodiments, the system controller 114 may receive input from sourcesincluding one or more of a blink detector, eye muscle sensors, and a fobcontrol. By way of generalization, it may be obvious to one skilled inthe art that the method of activating and/or controlling the systemcontroller 114 may require the use of one or more activation methods.For example, an electronic or powered contact lens may be programmablespecific to an individual user, such as programming a lens to recognizeboth of an individual's blink patterns and an individual's ciliarymuscle signals when performing various actions, for example, focusing onan object far away, or focusing on an object that is near. In someexemplary embodiments, using more than one method to activate anelectronic contact lens, such as blink detection and ciliary musclesignal detection, may give the ability for each method to becrosschecked with another before activation of the contact lens occurs.An advantage of crosschecking may include mitigation of false positives,such as minimizing the chance of unintentionally triggering a lens toactivate. In one exemplary embodiment, the crosschecking may involve avoting scheme, wherein a certain number of conditions are met prior toany action taking place.

The actuator 112 may comprise any suitable device for implementing aspecific action based upon a received command signal. For example, if ablink activation pattern is matched compared to a sampled light level asdescribed above, the system controller 114 may enable the actuator 112,such as a variable-optic electronic or powered lens. The actuator 112may comprise an electrical device, a mechanical device, a magneticdevice, or any combination thereof. The actuator 112 receives a signalfrom the system controller 114 in addition to power from the powersource 110 and produces some action based on the signal from the systemcontroller 114. For example, if the system controller 114 signal isindicative of the wearer trying to focus on a near object, the actuator112 may be utilized to change the refractive power of the electronicophthalmic lens, for example, via a dynamic multi-liquid optic zone. Inan alternate exemplary embodiment, the system controller 114 may outputa signal indicating that a therapeutic agent should be delivered to theeye(s). In this exemplary embodiment, the actuator 112 may comprise apump and reservoir, for example, a microelectromechanical system (MEMS)pump. As set forth above, the powered lens of the present invention mayprovide various functionality; accordingly, one or more actuators may bevariously configured to implement the functionality.

FIG. 3 illustrates a state transition diagram 300 for an exemplary blinkdetection system in accordance with the blink detection algorithm of thepresent invention. The system starts in an IDLE state 302 waiting for anenable signal bl_go to be asserted. When the enable bl_go signal isasserted, for example, by an oscillator and control circuit which pulsesbl_go at a one hundred (100) ms rate commensurate with the blinksampling rate, the state machine then transitions to a WAIT ADC state304 in which an ADC is enabled to convert a received light level to adigital value. The ADC asserts an adc_done signal to indicate itsoperations are complete, and the system or state machine transitions toa SHIFT state 306. In the SHIFT state 306 the system pushes the mostrecently received ADC output value onto a shift register to hold thehistory of blink samples. In some exemplary embodiments, the ADC outputvalue is first compared to a threshold value to provide a single bit (1or 0) for the sample value, in order to minimize storage requirements.The system or state machine then transitions to a COMPARE state 308 inwhich the values in the sample history shift register are compared toone or more blink sequence templates and masks as described above. If amatch is detected, one or more output signals may be asserted, such asone to toggle the state of the lens driver, bl_cp_toggle, or any otherfunctionality to be performed by the powered ophthalmic lens. The systemor state machine then transitions to the DONE state 310 and asserts abl_done signal to indicate its operations are complete.

FIG. 4 illustrates an exemplary photosensor or photodetector signal pathpd_rx_top that may be used to detect and sample received light levels.The signal path pd_rx_top may comprise a photodiode 402, atransimpedance amplifier 404, an automatic gain and low pass filteringstage 406 (AGC/LPF), and an ADC 408. The adc_vref signal is input to theADC 408 from the power source 110 (see FIG. 1) or alternately it may beprovided from a dedicated circuit inside the analog-to-digital converter408. The output from the ADC 408, adc_data, is transmitted to thedigital signal processing and system controller block 108/114 (see FIG.1). Although illustrated in FIG. 1 as individual blocks 108 and 114, forease of explanation, the digital signal processing and system controllerare preferably implemented on a single block 410. The enable signal,adc_en, the start signal, adc_start, and the reset signal, adc_rst_n arereceived from the digital signal processing and system controller 410while the complete signal, adc_complete, is transmitted thereto. Theclock signal, adc_clk, may be received from a clock source external tothe signal path, pd_rx_top, or from the digital signal processing andsystem controller 410. It is important to note that the adc_clk signaland the system clock may be running at different frequencies. It is alsoimportant to note that any number of different ADCs may be utilized inaccordance with the present invention which may have different interfaceand control signals but which perform a similar function of providing asampled, digital representation of the output of the analog portion ofthe photosensor signal path. The photodetect enable, pd_en, and thephotodetect gain, pd_gain, are received from the digital signalprocessing and system controller 410.

FIG. 5 illustrates a block diagram of digital conditioning logic 500that may be used to reduce the received ADC signal value, adc_data, to asingle bit value pd_data. The digital conditioning logic 500 maycomprise a digital register 502 to receive the data, adc_data, from thephotodetection signal path pd_rx_top to provide a held value on thesignal adc_data_held. The digital register 502 is configured to accept anew value on the adc_data signal when the adc_complete signal isasserted and to otherwise hold the last accepted value when theadc_complete signal is received. In this manner the system may disablethe photodetection signal path once the data is latched to reduce systemcurrent consumption. The held data value may then be averaged, forexample, by an integrate-and-dump average or other averaging methodsimplemented in digital logic, in the threshold generation circuit 504 toproduce one or more thresholds on the signal pd_th. The held data valuemay then be compared, via comparator 506, to the one or more thresholdsto produce a one-bit data value on the signal pd_data. It will beappreciated that the comparison operation may employ hysteresis orcomparison to one or more thresholds to minimize noise on the outputsignal pd_data. The digital conditioning logic may further comprise again adjustment block pd_gain_adj 508 to set the gain of the automaticgain and low-pass filtering stage 406 in the photodetection signal pathvia the signal pd_gain, illustrated in FIG. 4, according to thecalculated threshold values and/or according to the held data value. Itis important to note that in this exemplary embodiment six bit wordsprovide sufficient resolution over the dynamic range for blink detectionwhile minimizing complexity.

In one exemplary embodiment, the threshold generation circuit 504comprises a peak detector, a valley detector and a threshold calculationcircuit. In this exemplary embodiment, the threshold and gain controlvalues may be generated as follows. The peak detector and the valleydetector are configured to receive the held value on signaladc_data_held. The peak detector is further configured to provide anoutput value, pd_pk, which quickly tracks increases in the adc_data_heldvalue and slowly decays if the adc_data_held value decreases. Theoperation is analogous to that of a classic diode envelope detector, asis well-known in the electrical arts. The valley detector is furtherconfigured to provide an output value pd_vl which quickly tracksdecreases in the adc_data_held value and slowly decays to a higher valueif the adc_data_held value increases. The operation of the valleydetector is also analogous to a diode envelope detector, with thedischarge resistor tied to a positive power supply voltage. Thethreshold calculation circuit is configured to receive the pd_pl andpd_vl values and is further configured to calculate a mid-pointthreshold value pd_th_mid based on an average of the pd_pk and pd_vlvalues. The threshold generation circuit 504 provides the thresholdvalue pd_th based on the mid-point threshold value pd_th_mid.

The threshold generation circuit 504 may be further adapted to updatethe values of the pd_pk and pd_vl levels in response to changes in thepd_gain value. If the pd_gain value increases by one step, then thepd_pk and pd_vl values are increased by a factor equal to the expectedgain increase in the photodetection signal path. If the pd_gain valuedecreases by one step, then the pd_pk and pd_val values are decreased bya factor equal to the expected gain decrease in the photodetectionsignal path. In this manner the states of the peak detector and valleydetectors, as held in the pd_pk and pd_vl values, respectively, and thethreshold value pd_th as calculated from the pd_pk and pd_vl values areupdated to match the changes in signal path gain, thereby avoidingdiscontinuities or other changes in state or value resulting only fromthe intentional change in the photodetection signal path gain.

In a further exemplary embodiment of the threshold generation circuit504, the threshold calculation circuit may be further configured tocalculate a threshold value pd_th_pk based on a proportion or percentageof the pd_pk value. In a preferred exemplary embodiment the pd_th_pk maybe advantageously configured to be seven eighths of the pd_pk value, acalculation which may be implemented with a simple right shift by threebits and a subtraction as is well-known in the relevant art. Thethreshold calculation circuit may select the threshold value pd_th to bethe lesser of pd_th_mid and pd_th_pk. In this manner, the pd_th valuewill never be equal to the pd_pk value, even after long periods ofconstant light incident on the photodiode which may result in the pd_pkand pd_vl values being equal. It will be appreciated that the pd_th_pkvalue ensures detection of a blink after long intervals. The behavior ofthe threshold generation circuit is further illustrated in FIG. 9, asdiscussed subsequently.

FIG. 6 illustrates a block diagram of digital detection logic 600 thatmay be used to implement an exemplary digital blink detection algorithmin accordance with an embodiment of the present invention. The digitaldetection logic 600 may comprise a shift register 602 adapted to receivethe data from the photodetection signal path pd_rx_top, FIG. 4, or fromthe digital conditioning logic, FIG. 5, as illustrated here on thesignal pd_data, which has a one bit value. The shift register 602 holdsa history of the received sample values, here in a 24-bit register. Thedigital detection logic 600 further comprises a comparison block 604,adapted to receive the sample history and one or more blink templatesbl_tpl and blink masks bl_mask, and is configured to indicate a match tothe one or more templates and masks on one or more output signals thatmay be held for later use. The output of the comparison block 604 islatched via a D flip-flop 606. The digital detection logic 600 mayfurther comprise a counter 608 or other logic to suppress successivecomparisons that may be on the same sample history set at small shiftsdue to the masking operations. In a preferred exemplary embodiment thesample history is cleared or reset after a positive match is found, thusrequiring a full, new matching blink sequence to be sampled before beingable to identify a subsequent match. The digital detection logic 600 maystill further comprise a state machine or similar control circuitry toprovide the control signals to the photodetection signal path and theADC. In some exemplary embodiments the control signals may be generatedby a control state machine that is separate from the digital detectionlogic 600. This control state machine may be part of the digital signalprocessing and system controller 410.

FIG. 7 illustrates a timing diagram of the control signals provided froma blink detection subsystem to an ADC 408 (FIG. 4) used in aphotodetection signal path. The enable and clock signals adc_en,adc_rst_n and adc_clk are activated at the start of a sample sequenceand continue until the analog-to-digital conversion process is complete.In one exemplary embodiment the ADC conversion process is started when apulse is provided on the adc_start signal. The ADC output value is heldin an adc_data signal and completion of the process is indicated by theanalog-to-digital converter logic on an adc_complete signal. Alsoillustrated in FIG. 7 is the pd_gain signal which is utilized to set thegain of the amplifiers before the ADC. This signal is shown as being setbefore the warm-up time to allow the analog circuit bias and signallevels to stabilize prior to conversion.

FIG. 8 illustrates a digital system controller 800 comprising a digitalblink detection subsystem dig_blink 802. The digital blink detectionsubsystem dig_blink 802 may be controlled by a master state machinedig_master 804 and may be adapted to receive clock signals from a clockgenerator clkgen 806 external to the digital system controller 800. Thedigital blink detection subsystem dig_blink 802 may be adapted toprovide control signals to and receive signals from a photodetectionsubsystem as described above. The digital blink detection subsystemdig_blink 802 may comprise digital conditioning logic and digitaldetection logic as described above, in addition to a state machine tocontrol the sequence of operations in a blink detection algorithm. Thedigital blink detection subsystem dig_blink 802 may be adapted toreceive an enable signal from the master state machine 804 and toprovide a completion or done indication and a blink detection indicationback to the master state machine 804.

FIGS. 9A through 9G provide waveforms, FIGS. 9A-9G, to illustrate theoperation of the threshold generation circuit and automatic gain control(FIG. 5). FIG. 9A illustrates an example of photocurrent versus time asmight be provided by a photodiode in response to varying light levels.In the first portion of the plot, the light level and resultingphotocurrent are relatively low compared to in the second portion of theplot. In both the first and second portions of the plot a double blinkis seen to reduce the light and photocurrent. Note that the attenuationof light by the eyelid may not be one hundred (100) percent, but a lowervalue depending on the transmission properties of the eyelid for thewavelengths of light incident on the eye. FIG. 9B illustrates theadc_data_held value that is captured in response to the photocurrentwaveform of FIG. 9A. For simplicity, the adc_data_held value isillustrated as a continuous analog signal rather than a series ofdiscrete digital samples. It will be appreciated that the digital samplevalues will correspond to the level illustrated in FIG. 9B at thecorresponding sample times. The dashed lines at the top and bottom ofthe plot indicate the maximum and minimum values of the adc_data andadc_data_held signals. The range of values between the minimum andmaximum is also known as the dynamic range of the adc_data signal. Asdiscussed below, the photodetection signal path gain is different(lower) in the second portion of the plot. In general the adc_data_heldvalue is directly proportional to the photocurrent, and the gain changesonly affect the ration or the constant of proportionality. FIG. 9Cillustrates the pd_pk, pd_vl and pd_th_mid values calculated in responseto the adc_data_held value by the threshold generation circuit. FIG. 9Dillustrates the pd_pk, pd_vl and pd_th_pk values calculated in responseto the adc_data_held value in some exemplary embodiments of thethreshold generation circuit. Note that the pd_th_pk value is alwayssome proportion of the pd_pk value. FIG. 9E illustrates theadc_data_held value with the pd_th_mid and pd_th_pk values. Note thatduring long periods of time where the adc_data_held value is relativelyconstant the pd_th_mid value becomes equal to the adc_data_held value asthe pd_vl value decays to the same level. The pd_th_pk value alwaysremains some amount below the adc_data_held value. Also illustrated inFIG. 9E is the selection of pd_th where the pd_th value is selected tobe the lower of pd_th_pk and pd_th_mid. In this way the threshold isalways set some distance away from the pd_pk value, avoiding falsetransitions on pd_data due to noise on the photocurrent and adc_dataheld signals. FIG. 9F illustrates the pd_data value generated bycomparison of the adc_data_held value to the pd_th value. Note that thepd_data signal is a two-valued signal which is low when a blink isoccurring. FIG. 9G illustrates a value of tia_gain versus time for theseexample waveforms. The value of tia_gain is set lower when the pd_thstarts to exceed a high threshold shown as agc_pk_th in FIG. 9E. It willbe appreciated that similar behavior occurs for raising tia_gain whenpd_th starts to fall below a low threshold. Looking again at the secondportion of each of the FIGS. 9A through 9E the effect of the lowertia_gain is clear. In particular note that the adc_data_held value ismaintained near the middle of the dynamic range of the adc_data andadc_data_held signals. Further, it is important to note that the pd_pkand pd_vl values are updated in accordance with the gain change asdescribed above such that discontinuities are avoided in the peak andvalley detector states and values due solely to changes in thephotodetection signal path gain.

FIG. 10 illustrates exemplary light-blocking and light-passing featureson an integrated circuit die 1000. The integrated circuit die 1000comprises a light passing region 1002, a light blocking region 1004,bond pads 1006, passivation openings 1008, and light blocking layeropenings 1010. The light-passing region 1002 is located above thephotosensors (not illustrated), for example an array of photodiodesimplemented in the semiconductor process. In a preferred exemplaryembodiment, the light-passing region 1002 permits as much light aspossible to reach the photosensors thereby maximizing sensitivity. Thismay be done through removing polysilicon, metal, oxide, nitride,polyimide, and other layers above the photoreceptors, as permitted inthe semiconductor process utilized for fabrication or in postprocessing. The light-passing area 1002 may also receive other specialprocessing to optimize light detection, for example an anti-reflectivecoating, filter, and/or diffuser. The light-blocking region 1004 maycover other circuitry on the die which does not require light exposure.The performance of the other circuitry may be degraded by photocurrents,for example shifting bias voltages and oscillator frequencies in theultra-low current circuits required for incorporation into contactlenses, as mentioned previously. The light-blocking region 1004 ispreferentially formed with a thin, opaque, reflective material, forexample aluminum or copper already use in semiconductor wafer processingand post-processing. If implemented with metal, the material forming thelight-blocking region 1004 must be insulated from the circuitsunderneath and the bond pads 1006 to prevent short-circuit conditions.Such insulation may be provided by the passivation already present onthe die as part of normal wafer passivation, e.g. oxide, nitride, and/orpolyimide, or with other dielectric added during post-processing.Masking permits light blocking layer openings 1010 so that conductivelight-blocking metal does not overlap bond pads on the die. Thelight-blocking region 1004 is covered with additional dielectric orpassivation to protect the die and avoid short-circuits during dieattachment. This final passivation has passivation openings 1008 topermit connection to the bond pads 1006.

FIG. 11 illustrates an exemplary contact lens with an electronic insertcomprising a blink detection system in accordance with the presentembodiments (invention). The contact lens 1100 comprises a soft plasticportion 1102 which comprises an electronic insert 1104. This insert 1104includes a lens 1106 which is activated by the electronics, for examplefocusing near or far depending on activation. Integrated circuit 1108mounts onto the insert 1104 and connects to batteries 1110, lens 1106,and other components as necessary for the system. The integrated circuit1108 includes a photosensor 1112 and associated photodetector signalpath circuits. The photosensor 1112 faces outward through the lensinsert and away from the eye, and is thus able to receive ambient light.The photosensor 1112 may be implemented on the integrated circuit 1108(as shown) for example as a single photodiode or array of photodiodes.The photosensor 1112 may also be implemented as a separate devicemounted on the insert 1104 and connected with wiring traces 1114. Whenthe eyelid closes, the lens insert 1104 including photodetector 1112 iscovered, thereby reducing the light level incident on the photodetector1112. The photodetector 1112 is able to measure the ambient light todetermine if the user is blinking or not.

Additional embodiments of the blink detection algorithm may allow formore variation in the duration and spacing of the blink sequence, forexample by timing the start of a second blink based on the measuredending time of a first blink rather than by using a fixed template or bywidening the mask “don't care” intervals (0 values).

It will be appreciated that the blink detection algorithm may beimplemented in digital logic or in software running on amicrocontroller. The algorithm logic or microcontroller may beimplemented in a single application-specific integrated circuit, ASIC,with photodetection signal path circuitry and a system controller, or itmay be partitioned across more than one integrated circuit.

It is important to note that the blink detection system of the presentinvention has broader uses than for vision diagnostics, visioncorrection and vision enhancement. These broader uses include utilizingblink detection to control a wide variety of functionality forindividuals with physical disabilities. The blink detection may be setup on-eye or off-eye.

In accordance with another exemplary embodiment, the present inventionis directed to a powered or electronic ophthalmic lens having arear-facing pupil diameter sensor. The size of the pupils and changesthereof, namely, dilation and constriction, may be utilized to controlone or more aspects of the electronic or powered contact lens.

In other words, signals output from the pupil sensor may be input to asystem controller which in turn takes a specific action based upon theinput and outputs a signal to an actuator to implement a specificfunction. In addition, the sensed information may be utilized forevaluating medical conditions.

The iris is the partition between the anterior and posterior chambers ofthe eye. The iris is formed from two muscles that regulate the centralopening thereof, commonly referred to as the pupil. Similar to theshutter of a camera, the pupil, through the actions of the two muscles,controls the amount of light entering the eye. The size of the pupilvaries with age, the color of the iris, and refractive error if any;however, a number of other factors may affect the size of the pupils atany given time.

The pupils may become dilated from the use of certain agents, forexample, a cycloplegic drug such as atropine. The pupils may becomedilated as a result of paralysis of the third cranial nerve. The pupilmay be dilated and fixed to direct light stimulation and consensuallight stimulation after acute narrow-angle glaucoma. Alternately, thepupils may become constricted from the use of glaucoma medications suchas pilocarpine. Other drugs, for example, morphine, causes constrictionof the pupils. In addition, certain conditions, for example, iritis,interruption of the sympathetic pathways of the eye and irritativelesions of the cornea may also cause constriction or the pupils. Hippusis a spasmodic, rhythmic, but irregular dilation and constriction of thepupils and may be indicative of a number of conditions.

External psychic influences, including surprise, fear and pain alsocause the pupils to dilate. Dim light causes the pupils to dilatewhereas bright light causes the pupils to constrict. In addition, whenan individual focuses on a near distance object, for example, reading abook, the pupils converge and constrict slightly in what is commonlyreferred to as the accommodative reflex. Accordingly, since certainfactors are known to cause a specific pupilary reaction in otherwisehealthy eyes, sensing the reaction of the pupils may be utilized as acontrol means. For example, if pupil constriction is detected alone orin combination with convergence, then the system controller may send asignal to an actuator to change the state of a variable power-opticincorporated into the powered contact lens.

Referring now to FIG. 12, there is illustrated a powered contact lenswith a pupil diameter sensor. The contact lens 1200 is positioned on theeye 1201 of an individual. The iris of the eye 1201 is shown in twolevels of diameter, constricted 1203 and dilated 1205. The contact lens1200 covers a portion of the eye 1201 including the iris. The contactlens 1200 comprises a first exemplary pupil diameter sensor 1202 andelectronic component 1204. The contact lens 1200 may comprise otherdevices, not shown.

The exemplary pupil diameter sensor 1202 is preferably positioned in thecontact lens 1200 above the iris. As illustrated, the pupil diametersensor 1202 is a thin strip covering all possible pupil diameters whichpermits it to detect all levels of pupil diameter. If implemented as astrip, as in this exemplary embodiment, the strip is preferably thin andtransparent, so as to not disrupt light incident on the eye 1201. In oneexemplary embodiment, the pupil diameter sensor 1202 comprises an arrayof photodetectors facing back into or towards the iris. Depending on thepupil diameter, sensors at various distances from the center of the iriswill detect different reflected light. For example, when the iris isdilated most of the sensors may detect little light because of thelarge, dark pupil. Conversely, when the iris is constricted most sensorsmay detect higher light because of reflection off the iris. It should beappreciated that, for such a sensor, ambient light level and iris colormay need to be considered in the system design, for example, by aper-user programming and/or calibration. Such an ambient light sensormay be implemented as a forward-facing photosensor to complement therear-facing sensors of pupil diameter sensor 1202. To minimizedisruption of the optic zone in front of the eye, in one exemplaryembodiment the pupil diameter sensor 1202 may be implemented usingtransparent conductors such as indium-tin oxide and small, thin siliconphotosensors.

In an alternate exemplary embodiment, the pupil diameter sensor 1202 maybe implemented as an array of sensors positioned around the iris tomaximize coverage as opposed to just a linear strip. It should beappreciated that other physical configurations are possible to maximizeperformance, cost, comfort, acceptance, and other metrics.

The pupil diameter sensor 1202 may be integrated with other electronics,may function on its own, or may connect to another device such as acontroller portion of the electronic component 1204. In this exemplaryembodiment, the system controller samples the pupil diameter sensor 1202and, depending on results from the pupil diameter sensor 1202, mayactivate another component in the system (not shown). For example, thecontroller may activate a variable-focus lens. A power source (notshown) supplies current to the pupil diameter sensor 1202, thecontroller, and other components of the electronic ophthalmic system. Amore detailed description is given below.

Such a system may require not only detectors such as those illustratedand described, but also emitters (not shown). Such emitters may, forexample, comprise light-emitting diodes matched to the photosensors ofpupil diameter sensor 1202. Alternately, the emitters may comprisepiezoelectric ultrasonic transducers coupled to ultrasonic receivers inthe pupil diameter sensor 1202. In yet another exemplary embodiment, thesensors and emitters may create an impedance detection system, forexample, by passing a low-current signal through the eye and measuringchanges in voltage across the eye.

FIG. 13 illustrates a contact lens with an alternate exemplary pupildiameter sensor. The contact lens 1300 is positioned on the eye 1301 ofan individual. The iris of the eye 1301 is shown in two levels ofdiameter, constricted 1303 and dilated 1305. The contact lens 1300covers a portion of the eye 1301, including the iris. Rather than thestrip or array of detectors partially covering the pupil as describedabove and illustrated in FIG. 12, the system in FIG. 13 positions thepupil diameter sensor or sensors 1302 outside of the maximum pupildiameter 1305 but still inside the contact lens 1300. This configurationis beneficial because no obstruction of the optic zone occurs due to thepupil diameter sensor 1302. The pupil diameter sensor or sensors 1302may, for example, comprise a single- or multi-turn coil antenna. Such anantenna may receive electromagnetic radiation from the eye as themuscles controlling the iris contract and relax. It is well-known in therelevant art that muscle and neural activity of the eye may be detectedthrough changes in electromagnetic emissions, for example with contactelectrodes, capacitive sensors, and antennas. In this manner, a pupildiameter sensor based on a muscle sensor may be implemented. The pupildiameter sensor 1302 may also be implemented as one or more contact- orcapacitive electrodes designed to measure impedance across the eye.Similar to other proposed systems which use changes in impedance todetermine ciliary muscle activity in the eye, and hence a desire tochange focal state, impedance may be used to detect changes in pupildiameter. For example, the impedance measured across the iris and pupilmay change appreciably depending on pupil diameter. A pupil diametersensor 1302 placed at the appropriate location on the eye and properlycoupled to the eye could detect these changes in impedance and hencepupil diameter. The contact lens 1300 may also comprise an electroniccomponent 1304 as described above.

FIG. 14 illustrates an exemplary electronic system 1400 for controllingthe pupil diameter sensors, as illustrated in FIGS. 12 and 13, receivinginformation from them, and changing the state of an actuator. Pupildiameter sensor 1402 comprises one or more of the pupil diameter sensorsas previously described, for example, photosensors, antennas, orimpedance sensors. In this illustrated exemplary embodiment, anyemitters necessary to implement or improve the performance of thesensors are included in element 1402 for simplicity. Element 1402 maycomprise multiple sensors, or multiple sensor blocks such as 1402,perhaps implemented in different technologies and sensor methods.Element 1404 is an interface between the sensor 1402 and a digitalsystem controller 1406. Shown in one element 1404 for simplicity, thispart of the system is responsible for activating the sensor 1402,receiving information from it, converting from analog to digital,amplifying, filtering, processing, and any other necessary functions. Itmay comprise one or more of multiplexors, operational amplifiers,differential amplifiers, transimpedance amplifiers, analog-to-digitalconverters (ADC's), digital signal processors (DSP's), filters, andother devices as is know in the signal processing art. The output of thesignal conditioning element 1404 is a signal comprised of sensor datawhich is input to the system controller 1406. The system controller 1406considers inputs from the pupil diameter sensor 1402 and determines if astate change is necessary for actuator 1408. This actuator 1408 mayserve any one of a number of functions, for example, changing the stateof a variable-focus lens or the transmission of a filter in front of theeye. System controller 1406 may consider inputs from multiple sensors1402 and may drive multiple actuators 1408. A transceiver 1410 may beincluded in the system to send data to and/or receive data from externaldevices, for example a second contact lens mounted on the adjacent eye,spectacle lenses, a smartphone, or another device. Such communicationoccurs through an antenna 1412, perhaps an electromagnetic antenna or alight-emitting diode/photodiode sensor combination. A power source 1414,which may comprise a battery or energy harvester, powers the system.

It is important to note that communication with a device on the othereye as well as external lenses and sensors may be preferred to rule outcertain conditions which may act as false triggers for action. Forexample, if only one pupil is dilated, this might indicate a problemrather than simply low light.

In accordance with one exemplary embodiment, a digital communicationsystem comprises a number of elements which when implemented, may takeon any number of forms. The digital communication system generallycomprises an information source, a source encoder, a channel encoder, adigital modulator, a channel, a digital demodulator, a channel decoderand a source decoder.

The information source may comprise any device that generatesinformation and/or data that is required by another device or system.The source may be analog or digital. If the source is analog, its outputis converted into a digital signal comprising a binary string. Thesource encoder implements a process of efficiently converting the signalfrom the source into a sequence of binary digits. The information fromthe source encoder is then passed into a channel encoder whereredundancy is introduced into the binary information sequence. Thisredundancy may be utilized at the receiver to overcome the effects ofnoise, interference and the like encountered on the channel. The binarysequence is then passed to a digital modulator which in turn convertsthe sequence into analog electrical signals for transmission over thechannel. Essentially, the digital modulator maps the binary sequencesinto signal waveforms or symbols. Each symbol may represent the value ofone or more bits. The digital modulator may modulate a phase, frequencyor amplitude of a high frequency carrier signal appropriate fortransmission over or through the channel. The channel is the mediumthrough which the waveforms travel, and the channel may introduceinterference or other corruption of the waveforms. In the case of thewireless communication system, the channel is the atmosphere. Thedigital demodulator receives the channel-corrupted waveform, processesit and reduces the waveform to a sequence of numbers that represent, asnearly as possible, the transmitted data symbols. The channel decoderreconstructs the original information sequence from knowledge of thecode utilized by the channel encoder and the redundancy in the receiveddata. The source decoder decodes the sequence from knowledge of theencoding algorithm, wherein the output thereof is representative of thesource information signal.

It is important to note that the above described elements may berealized in hardware, in software or in a combination of hardware andsoftware. In addition, the communication channel may comprise any typeof channel, including wired and wireless. In wireless, the channel maybe configured for high frequency electromagnetic signals, low frequencyelectromagnetic signals, visible light signals and infrared lightsignals.

FIG. 15 illustrates ambient light 1502 and pupil diameter 1504 plottedversus time on the x-axis, illustrating how differences between thesetwo measured quantities could be used to activate an electronicophthalmic device such as a contact lens. During the first time period1501, ambient light level 1502 is increasing while pupil diameter 1504is decreasing. Ambient light and pupil diameter may be sensed aspreviously described, for example by a forward-facing photodiode and arear-facing impedance sensor, respectively. As is commonly the case, asambient light increases in time period 1501 pupil diameter decreases.This is a common reaction which occurs to maintain a relatively constantlight intensity on the retina by reducing the aperture of the iris. Intime period 1503, the ambient light level 1502 first continues toincrease then levels off. However, the pupil diameter 1504 constrictsmore rapidly than in the previous time period. This is not the classicalcorrelation between ambient light and pupil diameter. This response maybe caused by a narrow-angle response of the pupil, perhaps to a bookheld up close, versus the wide-angle response of an ambient lightdetector. In this manner, a change in pupil diameter response may bedetected and used to activate a function in an electronic ophthalmicdevice. In time period 1505, the ambient light 1502 continues flathowever the pupil diameter 1504 dilates or increases. Again, this may becaused by a specific response in the eye, for example, the accommodationreflex. In time period 1507 there is again a difference between ambientlight level 1502, which starts level then decreases, and pupil diameter1504 which stays flat. Again, this may be used to detect certainresponses in the eye and trigger changes in the operation of anelectronic ophthalmic device. Finally, in time period 1509 the classicalresponse is again observed similar to that shown in timer period 1501.As the ambient light level 1502 decreases, the pupil diameter 1504dilates to let in more light.

The activities of the signal conditioning block and system controller(1404 and 1406 in FIG. 14, respectively) depend on the available sensorinputs, the environment, and user reactions, for example the ambientlight level and pupil diameter as illustrated in FIG. 15. The inputs,reactions, and decision thresholds may be determined from one or more ofophthalmic research, pre-programming, training, and adaptive/learningalgorithms. For example, the general characteristics of pupil dilationversus ambient light may be well-documented in literature, applicable toa broad population of users, and pre-programmed into system controller1406. However, an individual's deviations from the general expectedresponse, for example the deviations illustrated in time periods 1503,1505, and 1507 of FIG. 15, may be recorded in a training session or partof an adaptive/learning algorithm which continues to refine the responsein operation of the electronic ophthalmic device. In one exemplaryembodiment, the user may train the device by activating a handheld fob,which communicates with the device, when the user desires near focus. Alearning algorithm in the device may then reference sensor inputs inmemory before and after the fob signal to refine internal decisionalgorithms. This training period could last for one day, after which thedevice would operate autonomously with only sensor inputs and notrequire the fob.

It should be appreciated that pupil diameter alone may be used totrigger changes in an electronic ophthalmic lens, for example increasingor decreasing the transmission of a variable-transmission lens in frontof the eye, or pupil diameter maybe be combined with one or more otherinputs to change the state of an electronic ophthalmic device.

It should also be appreciated that a device utilizing such a sensor maynot change state in a manner visible to the user; rather the device maysimply log data. For example, such a sensor could be used to determineif a user has the proper iris response throughout a day or if aproblematic medical condition exists.

In one exemplary embodiment, the electronics and electronicinterconnections are made in the peripheral zone of a contact lensrather than in the optic zone. In accordance with an alternate exemplaryembodiment, it is important to note that the positioning of theelectronics need not be limited to the peripheral zone of the contactlens. All of the electronic components described herein may befabricated utilizing thin-film technology and/or transparent materials.If these technologies are utilized, the electronic components may beplaced in any suitable location as long as they are compatible with theoptics.

Although shown and described in what is believed to be the mostpractical and preferred embodiments, it is apparent that departures fromspecific designs and methods described and shown will suggest themselvesto those skilled in the art and may be used without departing from thespirit and scope of the invention. The present invention is notrestricted to the particular constructions described and illustrated,but should be constructed to cohere with all modifications that may fallwithin the scope of the appended claims.

1. A powered ophthalmic lens, the powered ophthalmic lens comprising: acontact lens including an optic zone and a peripheral zone; and a pupildiameter sensor system incorporated into the contact lens for measuringpupil diameter, the pupil diameter sensor system including at least onesensor, a system controller operatively associated with the at least onesensor and configured for determining the diameter of the pupil andoutput a control signal based on pupil diameter, and at least oneactuator configured to receive the output control signal and implement apredetermined function.
 2. The powered ophthalmic lens according toclaim 1, wherein at least one sensor comprises a thin strip mountedacross the optic zone such that it can sense fully constricted and fullydilated pupils.
 3. The powered ophthalmic lens according to claim 2,wherein the thin strip comprises an array of photosensors mounted toface in towards the iris of the eye.
 4. The powered ophthalmic lensaccording to claim 3, wherein the array of photosensors comprisetransparent photosensors.
 5. The powered ophthalmic lens according toclaim 3, wherein the array of photodetectors comprise thin siliconphotosensors.
 6. The powered ophthalmic lens according to claim 1,wherein the at least one sensor comprises an array of individual sensorspositioned around the perimeter of the optic zone.
 7. The poweredophthalmic lens according to claim 6, wherein the array of individualsensors comprise photosensors.
 8. The powered ophthalmic lens accordingto claim 1, wherein the pupil dilation sensor further comprises a signalprocessor configured to receive signals from the at least one sensor,perform digital signal processing, and output one or more signals to thesystem controller.
 9. The powered ophthalmic lens according to claim 8,wherein the signal processor comprises associated memory.
 10. Thepowered ophthalmic lens according to claim 1, wherein the pupil diametersensor system comprises a power supply.
 11. The powered ophthalmic lensaccording to claim 1, wherein the at least one sensor comprises animpedance sensor.
 12. The powered ophthalmic lens according to claim 1,wherein the at least one sensor comprises a neuromuscular activitysensor.